Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Enviromental Physiology
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Enviromental Physiology
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Subject: Agricultural Science
Class: Senior Secondary 2
Term: 3rd Term
Week: 2
Theme: Animal Science
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explain the meaning of environmental physiology.
State the effects of changes in:Climate on growth, reproduction, egg production, etc.Temperature- control of heat/temperature Relative humidity-control of humidity.Light-control of light.
with good ventilation.
In Crop Production: Greenhouse Management: Using ventilation fans, dehumidifiers, or opening vents to reduce humidity in greenhouses.
Irrigation: For low humidity, regular irrigation helps maintain soil moisture, which plants transpire to regulate their internal humidity.
Mulching: Helps conserve soil moisture, thus indirectly contributing to local humidity around plants.
Spacing: Proper plant spacing to allow air circulation and reduce localized high humidity. 2.
5. Effects of Light and Control of Light Definition: Light refers to electromagnetic radiation, particularly visible light, which is crucial for biological processes. Key aspects are intensity (brightness), duration (photoperiod), and quality (wavelengths).
Effects on Organisms: Photosynthesis (Crops): Light is the energy source for photosynthesis, the process by which plants convert light energy into chemical energy. Light intensity, duration, and quality directly influence photosynthetic rates and, therefore, growth and yield.
Photoperiodism (Animals and Plants): This is the physiological response to the length of day or night.
Animals: Influences breeding cycles (e.g., sheep and goats are short-day breeders, poultry egg production is stimulated by longer day lengths), feathering, and melatonin production. Longer daylight hours (14-16 hours) stimulate egg production in chickens.
Plants: Influences flowering (long-day, short-day, and day-neutral plants).
Circadian Rhythms: Light helps regulate internal biological clocks in both animals and plants, affecting sleep-wake cycles, hormone release, and other daily physiological processes.
Control of Light: In Animal Husbandry (Poultry is a prime example): Artificial Lighting: Using incandescent or LED lights to extend day length, particularly to stimulate egg production in layers or rapid growth in broilers. For layers, a controlled light program (e.g., 16 hours light, 8 hours dark) is critical.
Blackout Curtains: In environmentally controlled houses, curtains can block out natural light to manipulate photoperiod for specific production goals (e.g., dark periods for broiler rest or to induce molting in layers).
Housing Design: Designing poultry houses with appropriate window sizes and orientation to optimize natural light entry while controlling intensity.
In Crop Production: Greenhouses/Shade Houses: Using transparent materials in greenhouses to maximize light for high-light-demanding crops, or shade nets in shade houses to reduce light intensity for sensitive crops (e.g., certain vegetables, nursery plants) in tropical regions.
Supplemental Lighting: In advanced horticulture, using artificial grow lights to extend photoperiod or compensate for low natural light, especially during cloudy seasons.
Plant Spacing: Ensuring proper plant spacing to allow adequate light penetration to lower leaves and prevent self-shading.
Pruning: Removing excess foliage to improve light penetration within the canopy. This section provides in-depth explanations of key concepts to enable the teacher to deliver the lesson effectively without external resources. 2.
1. Meaning of Environmental Physiology Environmental physiology is the study of how organisms (both plants and animals) respond and adapt to changes in their external environment. It focuses on the physiological processes (e.g., metabolism, respiration, reproduction, growth) within an organism and how these processes are influenced by environmental factors such such as temperature, humidity, light, climate, and soil conditions. In agricultural science, environmental physiology helps us understand how environmental stressors or optimal conditions affect the productivity, health, and survival of farm animals and crops. For instance, understanding how a chicken reacts to high temperatures helps a Nigerian poultry farmer design better housing. 2.
2. Effects of Changes in Climate on Farm Animals and Crops Climate refers to the long-term weather patterns of a region, including temperature, humidity, rainfall, and solar radiation. Changes in climate (e.g., global warming, increased frequency of droughts or floods) have significant impacts on agricultural productivity. a)
Growth: Animals: Extreme temperatures (very hot or very cold) reduce feed intake, increase energy expenditure for thermoregulation, and slow down metabolic processes, leading to reduced growth rates, poor weight gain, and increased time to market weight (e.g., broiler chickens take longer to reach market size during hot dry seasons). Water scarcity due to drought affects forage quality and availability, further limiting growth.
Crops: Changes in rainfall patterns (droughts or floods) directly impact water availability for photosynthesis and nutrient uptake, leading to stunted growth, reduced leaf area, and lower biomass production. Extreme temperatures can denature enzymes essential for growth, while prolonged cloud cover (reduced light intensity) limits photosynthesis. b)
Reproduction: Animals: Heat stress is a major inhibitor of reproduction in farm animals.
High temperatures can cause: Reduced libido in males (e.g., bulls, rams). Decreased semen quality and quantity (e.g., damage to sperm cells). Reduced conception rates in females (e.g., cows, goats) due to impaired ovulation, embryonic mortality, and hormonal imbalances. Increased incidence of abortion and stillbirths. Delayed onset of puberty or anestrus (absence of estrus cycle).
Example: During the peak of the dry season in Northern Nigeria, cattle breeders often observe lower fertility rates compared to cooler periods.
Crops: Climate change can disrupt flowering times, pollen viability, and seed setting. Extreme weather events (e.g., unseasonal rains) can wash away pollen or damage delicate floral structures, leading to reduced fruit or seed yield. c)
Milk Production: Animals (Dairy): Heat stress significantly reduces milk yield and quality in dairy animals like cows and goats.
This is because: Animals reduce feed intake to minimize metabolic heat production. Increased panting and sweating lead to water and electrolyte loss. Energy is diverted from milk synthesis to thermoregulation. Hormonal imbalances can affect mammary gland function.
Example: A Friesian cow in Lagos will produce less milk during the hot season than the same cow in a cooler environment or during the harmattan season, due to the physiological stress of dissipating heat. d)
Egg Production: Animals (Poultry): High environmental temperatures are detrimental to egg production in layers.
They cause: Reduced feed intake, leading to insufficient nutrient supply for egg formation. Decreased egg size and weight. Reduced eggshell quality (thinner, weaker shells) due to impaired calcium metabolism and respiration. Lowered egg production rate (fewer eggs laid). Increased mortality in severe heat stress conditions.
Example: A flock of Isa Brown layers in Ibadan during the hot season may show a drop in production from 90% to 70% or less, with many eggs having fragile shells. 2.
3. Effects of Temperature and Control of Heat/Temperature Definition: Temperature is the degree of hotness or coldness of an environment.
Effects on Organisms: Metabolic Rate: Each organism has an optimal temperature range for its metabolic processes. Outside this range, enzyme activity is affected. High temperatures can denature enzymes, while very low temperatures slow down metabolic reactions.
Water Balance: High temperatures increase water loss through evaporation (sweating, panting in animals; transpiration in plants), leading to dehydration.
Immune System: to 70% or less, with many eggs having fragile shells. 2.
3. Effects of Temperature and Control of Heat/Temperature Definition: Temperature is the degree of hotness or coldness of an environment.
Effects on Organisms: Metabolic Rate: Each organism has an optimal temperature range for its metabolic processes. Outside this range, enzyme activity is affected. High temperatures can denature enzymes, while very low temperatures slow down metabolic reactions.
Water Balance: High temperatures increase water loss through evaporation (sweating, panting in animals; transpiration in plants), leading to dehydration.
Immune System: Temperature stress can suppress the immune system, making animals and plants more susceptible to diseases.
Thermoregulation: Animals are either endotherms (warm-blooded, maintain constant body temperature, e.g., poultry, cattle) or ectotherms (cold-blooded, body temperature fluctuates with environment, e.g., fish, reptiles). Endotherms use energy to maintain body temperature, which can be significant under extreme conditions.
Control of Heat/Temperature: In Animal Husbandry: Shade: Providing natural (trees) or artificial (roofed shelters) shade.
Ventilation: Using fans, open-sided housing, or proper orientation of buildings to encourage air movement and heat dissipation (e.g., in poultry houses).
Misters/Foggers/Sprinklers: Especially for poultry and dairy animals, water spraying cools the environment and the animals through evaporative cooling.
Cooling Systems: Evaporative coolers or air conditioners (for high-value or highly sensitive animals, though less common in typical Nigerian farming due to cost).
Access to Cool Water: Ensuring a constant supply of fresh, cool drinking water.
Dietary Adjustments: Reducing feed density or feeding during cooler parts of the day.
Breeding: Selecting heat-tolerant breeds (e.g., local N'Dama cattle over exotic Friesians in hot zones).
In Crop Production: Irrigation: Supplying water to cool the plants and soil, and ensure water availability for transpiration.
Mulching: Covering the soil surface with organic material (straw, leaves) to reduce soil temperature and conserve moisture.
Shade Nets: For horticultural crops, using nets to reduce direct solar radiation and lower temperature.
Planting Times: Adjusting planting schedules to avoid extreme temperatures during critical growth stages.
Variety Selection: Choosing heat-tolerant crop varieties. 2.
4. Effects of Relative Humidity and Control of Humidity Definition: Relative humidity (RH) is the amount of moisture (water vapour) in the air expressed as a percentage of the maximum amount of moisture the air can hold at a given temperature.
Effects on Organisms: High Humidity: Animals: Reduces the efficiency of evaporative cooling (panting, sweating). When the air is saturated with moisture, it cannot absorb more water from the animal's body, making heat dissipation difficult and increasing heat stress. Also promotes fungal and bacterial growth, leading to respiratory problems and disease outbreaks (e.g., coccidiosis in poultry).
Crops: Increases the risk of fungal and bacterial diseases (e.g., blight, mildew). Reduces transpiration rates, which can indirectly affect nutrient uptake. Can lead to poor fruit setting or cracking in some crops.
Low Humidity: Animals: Increases evaporative water loss, leading to dehydration, especially if water intake is insufficient. Can cause dry skin and respiratory irritation.
Crops: Increases transpiration rates, potentially leading to wilting and drought stress if soil moisture is inadequate. Can lead to scorch or burn on leaves.
Control of Humidity: In Animal Husbandry: Ventilation: Good air circulation helps remove moist air, especially in enclosed spaces like poultry pens, reducing high humidity.
Proper Litter Management: Keeping litter dry by removing wet spots and ensuring proper bedding materials, especially in poultry houses, to reduce moisture accumulation and disease.
Misters/Foggers (controlled use): While they cool, over-application can increase humidity; they must be used judiciously, especially with good ventilation.
In Crop Production: Greenhouse Management: Using ventilation fans, dehumidifiers, or opening vents to reduce humidity in greenhouses.
Irrigation: For low humidity, regular irrigation helps maintain soil moisture, which plants transpire to regulate their internal humidity.
Mulching: Helps conserve soil moisture, thus indirectly contributing to local humidity around plants.
Spacing: Proper plant spacing to allow air circulation and reduce localized high humidity. 2.
5. Effects of Light and Control of Light Definition: Light refers to electromagnetic radiation, particularly visible light, which is crucial for biological 3.
1. Introduction (10 minutes)
Teacher Activity: Begin by asking students about recent weather changes they've observed in their locality (e.g., unusual heat, heavy rain, dry spell). Ask them to share how these changes might have affected local farms or their own observations of animals/plants. Introduce the concept of "Environmental Physiology" as the scientific study of these interactions.
Student Activity: Students share observations and participate in a brief discussion, making connections between weather and farming. 3.
2. Explanation and Discussion of Key Concepts (40 minutes)
Teacher Activity: Define environmental physiology clearly, using local examples (e.g., a farmer planning poultry housing in Kano vs. Jos). Explain the effects of climate changes on growth, reproduction, milk, and egg production, using charts or diagrams to illustrate concepts where possible. Provide concrete Nigerian examples (e.g., impact of harmattan on animals, dry season effects on rain-fed crops). Systematically explain the specific effects of Temperature, Relative Humidity, and Light, linking each to the performance objectives. For each factor, discuss the control mechanisms relevant to Nigerian farming practices. Facilitate questions and answers to ensure understanding.
Student Activity: Students listen attentively, take notes, and ask clarifying questions. Participate in discussions by relating concepts to their experiences or local farming practices. 3.
3. Group Activity / Case Study (25 minutes)
Teacher Activity: Divide students into small groups. Assign each group a scenario or challenge related to environmental factors in a Nigerian farming context.
Scenario 1:* A poultry farmer in Oyo State is experiencing a significant drop in egg production and increased mortality during the peak of the dry season.
Scenario 2:* A dairy farmer in Plateau State notices reduced milk yield and reproductive issues in his cows during the hottest months.
Scenario 3:* A vegetable farmer in Rivers State is struggling with fungal diseases on his tomatoes during the rainy season. Instruct each group to identify the primary environmental factor(s) at play and propose practical, cost-effective solutions for Nigerian farmers, drawing from the lesson.
Student Activity: Work in groups to discuss the assigned scenario, identify the problem, and brainstorm solutions based on the concepts learned. Each group selects a spokesperson to present their findings and proposed solutions to the class. 3.
4. Class Presentation and Wrap-up (15 minutes)
Teacher Activity: Oversee group presentations, provide feedback, and guide a summary discussion. Reinforce the importance of environmental management in agriculture.
Student Activity: Present group findings and engage in peer feedback and discussion.
Climate-Smart Agriculture and Adaptation: Understanding environmental physiology enables Nigerian farmers to adopt climate-smart agricultural practices. For instance, in areas prone to increasing heat waves (e.g., Northern Nigeria), farmers can choose heat-tolerant livestock breeds (e.g., N'Dama cattle instead of Friesian), use appropriate housing designs (open-sided, high roofs, proper orientation) to maximize natural cooling, and adjust feeding times to cooler periods of the day. This directly impacts their livelihoods by reducing losses due to environmental stress. Optimizing Animal Housing and Crop Field Management: The principles of environmental physiology are crucial for designing animal shelters (poultry pens, piggeries, cattle sheds) and managing crop fields. Farmers can decide on the best orientation for their structures to minimize sun exposure, use ventilation systems to control temperature and humidity, and implement irrigation schedules that account for temperature-induced water loss in crops. This leads to healthier animals, higher yields, and efficient resource use. For example, a farmer near Ibadan might decide to use a misting system in his poultry house during the dry season to prevent heat stress and maintain egg production. Breeding Programs and Seasonal Adjustments: Knowledge of how light (photoperiod) affects reproduction helps farmers manage breeding programs. For example, sheep farmers in Nigeria can anticipate the natural breeding season of their local breeds based on day length changes. Poultry farmers can use artificial lighting to maintain consistent egg production year-round, overcoming natural seasonal dips. This ensures a steady supply of agricultural products to the market and optimizes economic returns for farmers.